This is an alternative solution to Lee's "clk: Provide support for always-on clocks" series[0].
The first two patches introduce run-time checks to ensure that clock consumer drivers are respecting the clk.h api. The former patch checks for prepare and enable imbalances. The latter checks for calls to clk_put without first disabling and unpreparing the clk. The third patch introduces a new flag, CLK_ENABLE_HAND_OFF, which prepares and enables a clk at registration-time. The reference counts (prepare & enable) are transferred to the first clock consumer driver that clk_get's the clk with this flag set AND calls clk_prepare or clk_enable. The net result is that a clock with this flag set will be enabled at boot and neither the clk_disable_unused garbage collector or the "sibling clock disables a shared parent" scenario will cause the flagged clock to be disabled. The first driver to come along and explicitly claim, prepare and enable this clock will inherit those reference counts. No change to clock consumer drivers is required for this to work. Please continue to use the clk.h api properly. In time this approach can probably replace the CLK_IGNORE_UNUSED flag and hopefully reduce the number of users of the clk_ignore_unused boot parameter. Finally, a quick note on comparing this series to Lee's. I went with the simplest approach to solve a real problem: preventing critical clocks from being spuriously disabled at boot, or before a their parent clock becomes accidentally disabled by a sibling. All of the other kitchen sink stuff (DT binding, passing the flag back to the framework when the clock consumer driver calls clk_put) was left out because I do not see a real use case for it. If one can demonstrate a real use case (and not a hypothetical one) then this patch series can be expanded further. [0] http://lkml.kernel.org/r/<1437570255-21049-1-git-send-email-lee.jo...@linaro.org> Michael Turquette (3): clk: per-user clk prepare & enable ref counts clk: clk_put WARNs if user has not disabled clk clk: introduce CLK_ENABLE_HAND_OFF flag drivers/clk/clk.c | 79 +++++++++++++++++++++++++++++++++++++++++--- include/linux/clk-provider.h | 3 ++ 2 files changed, 78 insertions(+), 4 deletions(-) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
